bonjour
ABJ est un triangle rectangle en A
JB² = AJ² + AB²
JB² = 72² + 30 ² = 6 084
JB = √ 6 084 = 78 m
JM/JA = JU/JC = MU/AC
40/72 = 12 /AC
AC = ( 72 x 12 ) / 40 = 21.6 m
aire ABJ = ( 30 x 72 ) / 2 = 1 080 m²
aire ACJ = ( 21.6 x 72 ) / 2 = 777.6 ²
aire JCB = 1 080 - 777.6 = 302.4 m ²
